The present invention relates generally to an exhaust gas recirculation (EGR) control system for reducing the production of noxious components such as nitrogen oxides (NO.sub.x) in the combustion of an air-fuel mixture in an internal combustion engine by feeding exhaust gas of the engine through an EGR passageway into an intake passageway of the engine in which system an EGR control valve is operated by a vacuum from a port opening into the intake passageway just upstream of a throttle valve in its fully closed position and the vacuum is adjusted by atmospheric air the amount of which is controlled by the pressure of the engine exhaust gas in the EGR passageway, and particularly to an EGR control system of this type which is improved to comprise means for reducing and increasing the amount of the engine exhaust gas fed into the intake passageway during low and high load operations of the engine, respectively.
As is well known in the art, a conventional EGR control system of the above-mentioned type has been constructed in such a manner that during engine low load condition in which it is unnecessary to feed the engine exhaust gas into the intake passageway, an EGR control valve admits an excessive amount of engine exhaust gas into an intake passageway. This has resulted in the degradation of driveability of the engine and an increase in fuel consumption. Furthermore, the conventional EGR control system has been unable to feed a sufficient or necessary amount of engine exhaust gas into the intake passageway owing to a resistance to the flow of the engine exhaust gas in an EGR passageway upstream of the EGR control valve during engine high load condition. This has resulted in an increase in the production of nitrogen oxides.